This application claims priority of Taiwan Patent Application No. 90206008, filed on Apr. 17, 2001.
1. Field of the Invention
The invention relates to a cutting tool device for a wood planing machine, more particularly to a cutting tool device with planing knives that are firmly positioned thereon. Each of the planing knives has a cutting edge that is brought to be in point contact with the workpiece during operation.
2. Description of the Related Art
FIG. 1 shows a conventional cutting tool device for a wood planing machine. As shown, the conventional cutting tool device includes a knife driving shaft 1, a plurality of planing knives 2, and a plurality of tightening members 3.
The knife driving shaft 1 has an outer circumferential wall surface 101, and is provided with a plurality of insert grooves 102 angularly displaced from each other in the circumferential wall surface 101, and a plurality of shavings grooves 103 disposed proximate to a respective one of the insert grooves 102.
Each of the planing knives 2 has a cutting edge 201 projecting from the outer circumferential wall surface 101, and a blade portion 202 disposed in a respective one of the insert grooves 102.
Each of the tightening members 3 includes a threaded rod portion 301 that extends into a respective one of the insert grooves 102, and a head portion 302 for abutting against a respective one of the planing knives 2 in the respective one of the insert grooves 102.
During assembly, the planing knives 2 are respectively inserted into the insert grooves 102. Then, the tightening members 3 are respectively extended into the insert grooves 102 such that the head portions 302 thereof abut against the respective planing knife 2 to thereby position the planing knives 2 on the knife driving shaft 1.
Although the planing knives 2 of the conventional cutting tool device are positioned on the knife driving shaft 1, during planing of a workpiece, the planing knives 2, which are uprightly disposed in the insert grooves 102, may slip out from their respective insert groove 102. Besides, as the cutting edge 201 of each planing knife 2 is in linear contact with the workpiece, there exists an undesirably large frictional resistance to the cutting edge, which results in a heavy workload on an output shaft of a motor (not shown) and increased power consumption.
Therefore, the main object of the present invention is to provide a cutting tool device with planing knives that are firmly positioned thereon. Each of the planing knives has a cutting edge that is brought to be in point contact with the workpiece during operation.
Accordingly, a cutting tool device of the present invention is adapted for use in a wood planing machine, and includes an elongate knife driving shaft, a plurality of elongate planing knives, a plurality of tightening insert members, and a plurality of tightening members. The knife driving shaft is adapted to rotate in a counterclockwise operating direction about an axis, and includes left and right annular end wall surfaces opposite to each other in an axial direction parallel to the axis, and a cylindrical portion extending therebetween. The cylindrical portion has an outer circumferential wall surface surrounding the axis, and a plurality of insert receiving channels disposed to be angularly displaced from one another about the axis. Each of the insert receiving channels includes a knife seat wall surface and an abutment wall surface. The knife seat wall surface extends from the outer circumferential wall surface inwards and in the axial direction to form left and right end edges that join and intersect the left and right annular end wall surfaces, respectively. The left and right end edges respectively have left and right secant points at a respective junction with the outer circumferential wall surface. Each of the left and right end edges is configured such that an acute angle is formed between a respective one of the left and right end edges and a tangent line extending from a respective one of the left and right secant points rearwards in terms of the operating direction, and such that the left secant point lags behind the right secant point in the operating direction. The abutment wall surface extends from the outer circumferential wall surface inwards and in the axial direction to form left and right lateral edges that join the left and right annular end wall surfaces, respectively. The left and right lateral edges are configured to be spaced apart from the left and right end edges, respectively, so as to confine an accommodating cavity therebetween. The accommodating cavity extends radially and outwardly to communicate with the outer circumferential wall surface. Each of the planing knives includes front and rear major blade surfaces opposite to each other, and an elongate cutting edge which has left and right edge ends opposite to each other and joining the front and rear major blade surfaces. Each of the planing knives is disposed in a respective one of the insert receiving channels such that the front major blade surface is disposed to abut against the knife seat wall surface, such that the cutting edge is disposed to extend beyond the outer circumferential wall surface, such that the left and right edge ends are disposed to be adjacent to the left and right secant points, respectively, and such that the rear major blade surface faces towards the abutment wall surface. Each of the tightening insert members has front and rear mating wall surfaces opposite to each other in the operating direction, and is disposed to be removably inserted into the accommodating cavity to abut against the rear major blade surface of one of the planing knives and the abutment wall surface of one of the insert receiving channels, respectively. The tightening insert members are configured such that when a respective one of the tightening insert members is being inserted into the accommodating cavity radially and inwardly, a friction force generated as a result of sliding movement of the front mating wall surface along the rear major blade surface will impart a force component to the rear mating wall surface to cause the rear mating wall surface to abut against the abutment wall surface, thereby clamping the respective one of the planing knives between the front mating wall surface and the knife seat wall surface. The tightening members are disposed to threadedly secure the tightening insert members to the cylindrical portion respectively so as to ensure immobility of the planing knives.